Ichthyosaurs had a higher chance of being preserved than did terrestrial creatures because, as marine1 animals, they tended to live in environments less subject to erosion.

The quality of preservation2 is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing preserved embryos3.

After toiling4 up the Missouri all summer, the group wintered near the Mandan villages in the center of what is now North Dakata.

Lewis and Clark brought back much new information, including the knowledge that the continent was wider than originally supposed

Using only stone and wood tools, and without benefit of wheels or draft animals, the builders quarried5 ton upon ton of sandstone from the canyon6 walls, cut it into small blocks, hauled the blocks to the construction site, and fitted them together with mud mortar7.

The rocks of the crust are of very different ages. Some continental8 rocks are over 3,000 million years old, while those of the ocean floor are less than 200 million yeas old.

Given that two-thirds of the Earth’s surface is water and that marine lives at all levels of the ocean, the total three-dimensional living space of the ocean is perhaps 100 times greater than that of land and contains more than 90 percent of all life on Earth even though the ocean has fewer distinct species.

Science involves imagination and creative thinking as well as collecting information and performing experiments.

Science is built with facts just as a house I built with bricks, but a collection of facts cannot be called science any other than a pile of bricks can be called a house.

In the early nineteenth century, the knowledge of the physics of heat, which was essential to a science of refrigeration was rudimentary.

Rapid industrialization and increased geographic9mobility10 in the nineteenth century had special implications for women because these changes tended to magnify social distinctions.

Anthropology11 is a science in that anthropologists use a rigorous set of methods and techniques to document observations that can be checked by others.

With the growing prosperity brought on by the second world war and the economic boom that followed it , young people married and established households earlier and began to raise larger families than did their predecessors12 during the Depression.

These researchers have sought to demonstrate that their work can be a valuable tool not only of science but also of history, providing fresh insights into the daily lives of ordinary people whose existences might not otherwise be so well documented.

Technical difficulties aside, crow research is daunting13 because the ways of these birds are so complex and various.

Deeper still, the pressure is even more intense, preventing the rock from melting in spite of a higher temperature.

The range of the New York canal system was still further extended when the states of Ohio and Indiana, inspired by the success of the Eric Canal, provided water conncetions between Lake Eric and the Ohio River.

It is commonly believed that in the United States that school is where people to get an education. Nevertheless, it has been said that today children interrupt their education to to school. The distinction between schooling17 and education implied by this remark line is important.

The states encouraged internal improvements in two distinct ways: first, by actually establishing state companies to build such improvements; second, by providing part of the capital for mix public-private companies setting out to make a profit.

Per capita income is a nations entire income divided by the number of people in the nation.

Desert animals can drink prodigious18 volumes in a short time and camel have been kown to imbibe19 over 100 liters in a few minutes. A very dehydrated person, on the other hand, cannot drink enough water to hydrate at on session, because the human stomach is not sufficiently20 big and because a too rapid dilution21 of the body fluids causes death from water intoxication22. While still growing, crops belonged to the men who, in contrast to most other Native American groups, planted.

Barbed wire, first patented in the United States in 1867, played an important part in the development of American farming, as it enabled the setters to make effective fencing to enclose their land and keep cattle away from their crops.

The pressure exerted on the human body increases by 1 atmosphere for every 10 meters of depth in seawater, so that a 30 meters in seawater a diver is exposed to a pressure of about 4 atmospheres.

During ascent23 from a depth of 10 meters, the volume of air in the lungs will double because the air pressure at the surface is only half of what it was at 10 meters.

Beads24 were probably the first durable25ornaments26 humans possessed27 and the intimate relationship they had with their owners is reflected in the fact that beads are among the most common items found in ancient archaeological side.

As a rule, large billed crossbills are better at seeming seeds from large cones28 while small billed crossbills are more deft29 at removing seeds from small, thin scaled cones. Moreover, the degree to which cones are naturally slightly open on tightly closed determine which bill design is the best.

By comparison with these familiar yardsticks30, the distances to the galaxies31 are incomprehensibly large ,but they too are made more manageable by using a time calibration, in this case the distance that light travels in one year.

The argument that humans ,even in prehistoric32 times, had some number sense, at least to the extent of recognizing the concepts of more and less when some objects were added to or taken away from a small group. seems fair. for studies have shown that some animal possess such a sense.

On a global basis, nature’s output of these compounds dwarfs33 that resulting from human activities. However, human production usually occurs in a localized area, such as a city.

The actual concentration need not be large for a substance to be a pollutant34 in fact the numerical value tell us little until we know how much of an increase this presents over the concentration that would occur naturally in the area. Sulfur35 dioxide, for example, has detectable36 health effects at 0.08 parts per millia (ppm),which is about 400 times its natural level .Carbon monoxide, however, has a natural level of 0.1 ppm and is not naturally a pollutant until its level reaches about 15 ppm.

The acute, growing public awareness37 of the social changes that had been taking place for some time was tied to tremendous growth in popular journalism38 in the late nineteenth century, including growth in quantity and circulation of both magazines and newspapers. These developments, in addition to the continued growth of cities, were significant factors in the transformation39 of society from one characterized by relatively40, isolated41 self-contained communities into an urban, industrial nation.

Another unusual feature of glass id the manner in which its viscosity42 changes as it turns from a cold substance into a hot, ductile43 liquid. Unlike metals that flow or “freeze” at specific temperatures, glass progressively softens44 as the temperature malleability45 until it flows like a thick syrup46.

Footprints thus provide us not merely with rare impressions of the soft tissue of early hominids, but also with evidence of upright walking that in many ways is clearer that can be obtained from the analysis of bones.

The tight arrangement enabled the Mandans to protect themselves more easily from the attacks of others who might seek to obtain some of the food these highly capable farmers stored from one year to the next.

The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.

Farm dwellers47 in their isolation48 not only found it harder to locate companions in play but also, thanks to the unending demands and pressures of their work, felt it necessary to combine fun with purpose.

When a neighbor needed help, families rallied form miles around to assist in building a house a barn, husking corn shearing49, or chopping wood.

Certainly, these have been periods in Earth’s history when mass extinctions have occurred. The extinction50 of dinosaurs51 was caused by some physical event, either climatic or cosmic. However, nothing has ever equaled the magnitude and speed with the human species is altering the physical and chemical world and demolishing52 the environment. In fact, there is wide agreement that it is the change humans are inflicting53 even more than the changes of themselves, that will lead to biological devastation54.

There is little doubt that one reason why the number of amphibians56 is declining is that their habitats are being destroyed.

Other factors that could be contributing to the decline include acid rain and the spread of the pesticide57residue58.

Water can pass through the amphibian55 skins, allowing the toxins59 dissolved in the water to enter the amphibians body.

We, take for granted some of the other inventions that enable people to live and work in skyscrapers60.

In some places of Texas, water levels have declined by more than 400 feet in twenty five years.

Freight trains have an accident rate that is only 1/2 that of the tracking industry.

Trains also come out a heat of the trucks on environmental grounds because they give off only 1/10 to 1/3 the pollution that is emitted by trucks.

With bicycle chains covered, cyclists would need to clean and oil their trains once every month instead of once a week.

Despite his invention, however, she still advises cyclists to take a taxi or bus when it is snowing heavily. Not because the condition are too arduous61 for bicycles, but because believes bikers can not have confidence in the people who drive cars on days of reduced visibility.

In preparing to climb, you learn patience mental discipline and you gain fantastic physical strength especially in your hands.

But ligin is acidic and its presence in paper has shorten the life expectancy62 of paper from several centuries for rag paper to less than a century for paper made from wood pulp63.

But while wood pulp solved the problem of quantity, it created a problem of quality.

In warm-blooded animals birds and mammals for example, the body temperature normally stays within a narrow range no matter what the outside temperature is.

This new pose stressed the relationship between dinosaurs and modern birds and supports the theory that dinosaurs actually more closely related to birds than to any other exsting creature.

They lived in what is now Arizona from 300 B.C to AD 1500.

Which view is correct? Well, historians who wrote during the calm and prosperous 1950s found reasons to the idealist view. Those who wrote during the trouble of 1960s found supports for economic view point. I would say that neither view is complete, both the idealist and the economic perspective contribute a part to the whole picture.